A Structure Hierarchy for the Aluminofluoride Minerals

2021 ◽  
Author(s):  
Frank C. Hawthorne ◽  
Sasha Herwig
Keyword(s):  
Chemical Composition ◽  
Bond Valence ◽  
Lewis Acidity ◽  
Crystal Chemical ◽  
Structural Group ◽  
Coordination Polyhedra ◽  
Structural Hierarchy ◽  
Anionic Groups ◽  
Complex Anions

ABSTRACT The structure hierarchy hypothesis states that structures may be ordered hierarchically according to the polymerization of coordination polyhedra of higher bond-valence, and such hierarchies are useful in understanding the general compositional, structural, and paragenetic variations within the structural group of interest. Here we develop a structure hierarchy for the aluminofluoride minerals based on the polymerization of the dominant (AlΦ6) octahedra and their linkage with other strongly bonded complex anionic groups. The minerals are divided first into the following categories: (1) simple aluminofluorides and (2) compound aluminofluorides containing other oxyanions. The minerals are then ordered according to the polymerization of the constituent polyhedra into a coherent structural hierarchy. The chemical composition and crystal-chemical details of the ions of the interstitial complex are a collective function of the Lewis acidity of the interstitial cations; the presence of interstitial anions, both simple [F–, (OH)–] and complex [(SO4)2–]; self-polymerization of the (AlF6)3– octahedra; and polymerization with both Mg(F,OH)6 octahedra and other complex anions: (SO4)2–, (PO4)3–, (CO3)2–.

The structure of antimonian dussertite and the role of antimony in oxysalt minerals

1999 ◽  
Vol 63 (1) ◽  
pp. 17-26 ◽  
Author(s):  
U. Kolitsch ◽  
P. G. Slade ◽  
E. R. T. Tiekink ◽  
A. Pring
Keyword(s):  
Hydrogen Bonding ◽  
Electron Microprobe ◽  
Structure Refinement ◽  
Bond Valence ◽  
Crystal Chemical ◽  
Coordination Polyhedra ◽  
Space Group ◽  
Bond Lengths ◽  
The Mean

AbstractThe structure of antimonian dussertite, (AsO4)2(OH,H2O)6, has been refined in space group R3̄m with a 7.410(3), c 17.484(4) Å, Z = 3, to R = 3.2 % and Rw = 3.7 % using 377 observed reflections with I ≥ 3 σ(I). The structure is of the alunite-type and consists of sheets of corner-sharing (Fe3+,Sb5+)O6 octahedra parallel to (0001). The substitution of Sb5+ for Fe3+, and not for As5+, is unambiguously demonstrated not only by the structure refinement but also by electron microprobe analyses and crystal-chemical considerations. The icosahedrally coordinated Ba cations occupy cavities between pairs of octahedral sheets and are surrounded by six O atoms from the AsO4 tetrahedra and six O atoms from the (Fe3+,Sb5+)O6 octahedra. The mean bond lengths for the various coordination polyhedra are As-O 1.684(3) Å, (Fe,Sb)-O 2.004(1) Å, and Ba-O 2.872(2) Å. A hydrogen-bonding network is modelled using bond-valence calculations. The dussertite sample investigated is the first member of the crandallite group found to contain substantial Sb.

The pseudomalachite-ludjibaite-reichenbachite conundrum: OD description

2019 ◽  
Vol 57 (5) ◽  
pp. 571-581
Author(s):  
Emil Makovicky
Keyword(s):  
Crystal Structures ◽  
Current Knowledge ◽  
The Other ◽  
Crystal Chemical ◽  
Layer System ◽  
Coordination Polyhedra

Abstract Crystal structures of the three polymorphs of Cu5(PO4)2(OH)4, namely pseudomalachite, ludjibaite, and reichenbachite, can be described as being composed of rods perpendicular to their crystal-chemical layering. Two different sorts of rods can be defined. Type 1 rods share rows of Cu coordination polyhedra, forming a series of slabs. Slab boundaries and slab interiors represent alternating geometric OD layers of two kinds, with layer symmetries close to P21/m and , which make up two different stacking schemes of geometric OD layers in the structures of ludjibaite and pseudomalachite. Such OD layers, however, are not developed in reichenbachite. Type 2 rods are defined as having columns of PO4 tetrahedra in the corners of the rods. In the Type 2 slabs composed of these rods, geometric Pg OD layers of glide-arrayed tetrahedra alternate with more complex OD layers; in ludjibaite this system of layers is oriented diagonally with respect to the Type 1 OD layer system. Two different OD stackings of Type 2 OD layers form the ludjibaite and reichenbachite structures but not that of pseudomalachite. Thus, ludjibaite might form disordered intergrowths with either of the other two members of the triplet but reichenbachite and pseudomalachite should not form oriented intergrowths. Current knowledge concerning formation of the three polymorphs is considered.

Influence of polyhedron distortions on calculated bond-valence sums for cations with one lone electron pair

2007 ◽  
Vol 63 (2) ◽  
pp. 216-228 ◽  
Author(s):  
X. Wang ◽  
F. Liebau
Keyword(s):  
Periodic System ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Correlation Equations ◽  
Coordination Polyhedra ◽  
Absolute Value ◽  
Whole Number ◽  
Correlation Parameters ◽  
Bond Valence Model

In the present bond-valence model (BVM), the bond-valence parameters r 0 and b are, in general, supposed to be constant for each A–X pair and equal to 0.37 Å for all A–X pairs, respectively. For [A i (X j ) n ] coordination polyhedra that do not deviate strongly from regularity, these suppositions are well fulfilled and calculated values for the bond-valence sums (BVS) i are nearly equal to the whole-number values of the stoichiometric valence. However, application of the BVM to 2591 [L i (X j ) n ] polyhedra, where L are p-block cations, i.e. cations of the 13th to 17th group of the periodic system of elements, with one lone electron pair and X = O−II, S−II and Se−II, shows that r 0i values of individual [LX n ] polyhedra are correlated with the absolute value |Φ i | of an eccentricity parameter, Φ i , which is higher for more distorted [LX n ] polyhedra. As a consequence, calculated (BVS) i values for these polyhedra are also correlated with |Φ i |, rather than being numerically equal to the stoichiometric valence of L. This is interpreted as the stereochemical influence of the lone electron pair of L. It is shown that the values of the correlation parameters and the R 2 values of the correlation equations depend on the position of the L cation in the periodic system of elements, if the correlations are assumed to be linear. This observation suggests that (BVS) L describes a chemical quantity that is different from the stoichiometric valence of L.

Analysis of the environment of beryllium, magnesium and alkaline earth atoms in oxygen-containing compounds

1999 ◽  
Vol 55 (2) ◽  
pp. 139-146 ◽  
Author(s):  
V. A. Blatov ◽  
L. V. Pogildyakova ◽  
V. N. Serezhkin
Keyword(s):  
Crystal Structure ◽  
Alkaline Earth ◽  
Organometallic Compounds ◽  
Alkaline Earth Metals ◽  
The Other ◽  
Crystal Chemical ◽  
Coordination Polyhedra ◽  
Coordination Numbers ◽  
Coordination Spheres

About 2100 inorganic and organometallic compounds containing beryllium, magnesium and alkaline earth atoms (M) were investigated with Voronoi–Dirichlet polyhedra (VDPs). It is shown that the coordination numbers (CNs) of the M atoms in MO n coordination polyhedra can be determined by means of VDPs without crystal-chemical radii. The distributions of the M—O distances in the coordination spheres of the M atoms are bimodal for M = Be or Mg and monomodal for the other alkaline earth metals. Beryllium and magnesium coordination polyhedra containing weak M—O contacts were classified by variants of their distortions. It is found that the volume of the domains of the Mg, Ca, Sr and Ba atoms is independent of their CNs at CN \ge 6 (up to 16 for barium). The possibility of using the model of deformable spheres to describe the crystal structure of the compounds investigated is suggested.

NEPTUNYL COMPOUNDS: POLYHEDRON GEOMETRIES, BOND-VALENCE PARAMETERS, AND STRUCTURAL HIERARCHY

2008 ◽  
Vol 46 (6) ◽  
pp. 1623-1645 ◽  
Author(s):  
T. Z. Forbes ◽  
C. Wallace ◽  
P. C. Burns
Keyword(s):  
Bond Valence ◽  
Structural Hierarchy

Crystal chemistry of ettringite

1962 ◽  
Vol 33 (256) ◽  
pp. 59-64 ◽  
Author(s):  
Duncan McConnell ◽  
Joseph Murdoch
Keyword(s):  
Crystal Chemistry ◽  
Simple Form ◽  
Unit Cell ◽  
Crystal Chemical ◽  
Aluminium Sulphate ◽  
Hexagonal Unit Cell ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Anionic Groups ◽  
Oxygen Atoms

Summary Crystal-chemical calculations are based on three chemically analysed samples of ettringite and their respective unit-cell dimensions and specific gravities. The large hexagonal unit cell is deduced to contain 384 oxygen atoms, 64 cations with co-ordination number 6 or more, and 48 cations with co-ordination number 4 or less. Some substitution of cations with co-ordination number 3 apparently takes place, and any excess above 192 H2O takes place in the form of substitution of (H4O4) for XO4 anionic groups. The isomorphism is extremely complex but can be generalized in simple form as 16[A4(XO4)3(H2O)12], where A represents atoms with six-fold co-ordination (Ca, Na, Al) and X represents atoms with four-fold coordination (S, Si, H4, and possibly some of the Al). It is implied that an isostructural series of silicon-containing calcium aluminium sulphate hydrates might exist, the extreme compositions of which are: 6CaO.Al2O3.3SO3.3SiO2.24H2O and 6CaO.Al2O3.3SO3.30H2O.

COTTONWEED MARSH (MARSH). CHEMICAL COMPOSITION OF ETHANOL EXTRACT

2020 ◽  
Vol 5 (4) ◽  
pp. 29-32
Author(s):  
V. Platonov ◽  
V. Dunaev ◽  
G. Suhih ◽  
M. Shatskiy ◽  
M. Volochaeva
Keyword(s):  
Chemical Composition ◽  
Mass Spectra ◽  
Ethanol Extract ◽  
Structural Group ◽  
Quantitative Content ◽  
Wide Range ◽  
Structural Formulas ◽  
First Time ◽  
Sulfur Containing

For the first time, a detailed study of the chemical composition of ethanol extract of dried marsh (swamp), a product obtained after preliminary exhaustive last ex-traction with n-hexane, toluene, chloroform and acetone was performed. Chromatography-mass spectrometry made it possible to identify 119 individual compounds in this extract with the determination of their quantitative content, mass spectra and structural formulas, and the calculation of the structural-group composition was performed. A characteristic feature of the extract is the presence of significant amounts of nitrogen and sulfur-containing compounds (20.04), esters (21.47), sterols (18.54), carboxylic acids (8.15) and hydrocarbons (7.15) (wt. % of the extract). In addition, the extract contains phenols, ketones, aldehydes, alcohols and glycosides: 5.01; 4.34; 4.88; 3.16 and 3.12 (wt. % of the extract), respectively. Dominance in the extract of nitrogen-sulfur-containing and compounds; environment of sterols-betulin and its derivatives, esters, as well as the presence of different structure of phenols, glycosides, aldehydes and alcohols makes it possible to assume a wide range of pharmacological activity of drugs based on ethanol extract of dried marsh (marsh).

scholarly journals Design of Metal-Organic Polymers MIL-53(M3+): Preparation and Characterization of MIL-53(Fe) and Graphene Oxide Composite

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1281
Author(s):  
Quang K. Nguyen ◽  
Galina M. Kuz’micheva ◽  
Evgeny V. Khramov ◽  
Roman D. Svetogorov ◽  
Ratibor G. Chumakov ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
Structural Characteristics ◽  
Crystal Chemical ◽  
Organic Polymers ◽  
Crystal Chemical Analysis ◽  
Coordination Polyhedra ◽  
X Ray ◽  
Composition And Structure ◽  
Metal Organic

This article presents a crystal chemical analysis, generalization, and systematization of structural characteristics of metal-organic polymers MIL-53(M3+) with M = Al, Cr, Ga, and Fe. The division of the MIL-53(M3+) structures into a morphotropic series was performed, which made it possible to predict the formation of new compounds or solid solutions with the corresponding composition and structure. The change in the symmetry of MIL-53(M3+) and the causes of polymorphs formation are explained on the basis of crystal chemical rules. The efficiency of the revealed regularities in the structural characteristics of the MIL-53(M3+) phases were experimentally confirmed for MIL-53(Fe) and composite MIL-53(Fe)/GO (GO-graphene oxide) by several methods (powder X-ray, X-ray absorption, and photoelectron spectroscopy). For the first time, different coordination numbers (CN) (CNFe = 4.9 for MIL-53(Fe)—two types of coordination polyhedra with CNFe = 6 and CNFe = 4; CNFe = 4 for MIL-53 (Fe3+)/GO) and the formal charges (FC) of iron ions (variable FC of Fe (2+δ)+ in MIL-53(Fe3+) and Fe2+ in MIL-53(Fe3+)/GO) were found. These experimental data explain the higher photocatalytic activity of MIL-53(Fe3+)/GO in photo-Fenton reactions—RR195 decomposition.

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